Travis: don't generate git clone progress for logs

The logs are usually not looked at, and when they are it's almost
always after they've completed and returned a status.  That being
the case, "progress" output is useless if it's always seen after
the fact.

Signed-off-by: Philip Prindeville <[email protected]>

Reviewed-by: Andy Polyakov <[email protected]>
Reviewed-by: Rich Salz <[email protected]>
(Merged from openssl#6928)

.travis.yml

@@ -7,6 +7,7 @@ language: c
 cache: ccache
 git:
     submodules: false
+    quiet: true
 
 before_install:
     - if [ -n "$COVERALLS" ]; then